Tracing linen 24 Inks 25 Drawing pens 25 Pencils 25 Rubber erasers and cleaners 25 Colored pencils and crayons 26 Water colors 26 Japanese transparent water colors 26 Coloring geologic maps 27 Diagrams 28 Essential features 28 Plans of mine workings 29 Sections 29 Lithologic symbols 32 Use of photographs as illustrations 32 Essential features 32 Copyrighted photographs 33 Sources of photographs 34 Lending original photographs and drawings 34 Unpublished photographs 34 Specimens 34 General requirements 34 Borrowed and fragile specimens 35 Transmittal of paleontologic specimens 35 Making up plates 36 Reuse of illustrations 37 Approval of finished illustrations 38 Revision of illustrations 38 Submittal of proofs 38 Proof-reading illustrations 39 General considerations 39 Part II. Preparation by Draftsmen.